The present invention comprises a method of using 4-amino-8-phenyl-N-propyl-3-cinnolinecarboxamide to bind to benzodiazepine receptors, which method may be useful in the antagonism of certain pharmacological effects of benzodiazepine agonists. This method may also be useful as a biochemical tool in characterizing the action of other chemical compounds.
It is well know that compounds which are agonists at benzodiazepine receptors have utility as antianxiety agents and have sedative, muscle relaxant and anticonvulsant properties, as well. Such agents include, for example, chlordiazepoxide, diazepam, lorazepam, prazepam, halazepam, oxazepam, chlorazapate, alprazolam, flurazepam, triazolam, temazepam and the like. While the first discovered compounds with such properties contained the benzodiazepine ring system, other compounds not sharing that ring system have also been discovered which bind to benzodiazepine receptors and show agonistic activity. In addition, compounds are known which bind the benzodiazepine receptor and exhibit "inverse agonist" activity with potential utility as, for example, ethanol antagonism, cognition activation and appetite suppression. A benzodiazepine antagonist, i.e. a compound which binds the benzodiazepine receptor without activating it, will competitively reverse the activity of a benzodiazepine receptor agonist or inverse agonist at that receptor. The need for and utility of benzodiazepine receptor antagonists are well recognized and described, see, for example, U.S. Pat. Nos. 4,595,684: 4,666,903 and 4,713,383. As with agonists and inverse agonists, compounds containing the benzodiazopine ring system and compounds not containing it have been found to be effective benzodiazepine antagonists. The most widely investigated and well known is ethyl 8-fluoro-5, 6-dihydro-5-methyl-6-oxo-4H-imidazo(1,5a)(1,4)benzodiazepine-3-carboxylate (also known as Ro 15-1788, flumazenil and flumazepil) which is marketed in several nations, see, for example, New Drug Commentary, 12(12):16-17 (1985); Drugs Today, 23, 307 (1987).
Selected cinnoline compounds including selected 4-amino- and 4-oxo-cinnoline-3-carboxamides are disclosed in East German Pat. No. 123525 (Verfahren zur Herstellung von substituierten 4-Aminocinnolinen): U.S. Pat. No. 4,379,929 to Conrad et al: Daunis et al., "Preparation et proprietes de cinnolones-3 et cinnolones-4," Bull. de la Societe Chimique de France, 8:3198-3202 (1972): Lunt et al. "A New Cinnoline Synthesis," J. Chem. Soc. (C), 687-695 (1968): Gewald, et al., "Synthese von 4-Aminocinnolinen aus (Arylhydrazono)(cyan)-essigsaurederivaten," Liebigs Ann. Chem., 1390-1394 (1984): and U.S. Pat. No. 3,657,241 to Kurihara. Additionally, selected cinnoline compounds, including 3-acyl-4-substituted cinnoline derivatives are disclosed in Liebigs Ann. Chem. 1390-1394 (1984) supra and Sandison, et al., "A New Heterocyclisation Reaction Leading to Cinnolin-4(1H)-one Derivatives," J. Chem. Soc. Chem. Comm., 752-753 (1974).
Cinnoline compounds including that of the present invention which are amide and ester derivatives of 4-substituted cinnoline-3-carboxylic acids and 3-acyl-4-substituted-cinnoline derivatives are described in European Application Publication No. 205272 A2 (hereinafter called the EPO Application) and assigned to the same assignee as this invention. This EPO Application discloses cinnolines of the following formula (I):
(Formula set out on pages following Examples) I
wherein:
R.sup.3 is an amide of the formula (II): ##STR2## an ester of the formula (III): ##STR3## or a ketone of the formula (IV): ##STR4## R.sup.4 is --NR.sup.12 R.sup.13 or --OR.sup.12 ; R.sup.5, R.sup.6, R.sup.7 and R.sup.8 may be the same or different and are each hydrogen, (1-10C)alkyl, (2-10C)alkenyl, (2-10C)alkynyl, (3-6C)cycloalkyl, (4-10C)cycloalkylalkyl, (1-10C)aryl, (1-10C)substituted aryl, (2-11C)arylalkyl, (2-11C)(substituted aryl)alkyl, (1-10C)fluoroalkyl having at least one fluorine, (2-10C)haloalkenyl having at least one halogen, (2-10C)alkoxyalkyl, (1-10C)hydroxyalkyl, halogeno, (1-10C)alkoxy, (3-10C)alkenyl-oxy, hydroxy, nitro, cyano or amino including substituted amino; PA0 R and R.sup.9 may be the same or different and may each be hydrogen (provided that R.sup.3 is not an ester of formula III) except that R and R.sup.9 cannot both be hydrogen at the same time, (1-10C)alkyl, (3-10C)alkenyl, (3-10C)alkynyl, (3-6C)cycloalkyl, (4-10C)(cycloalkyl)alkyl, (1-10C)aryl, (1-10C)substituted aryl, (2-11C)arylalkyl, (2-11C)(substituted aryl)alkyl, 4,5-dihydro-2-thiazolyl of the following formula (V): PA0 (Formula set out on pages following Examples) V (2-10C)alkoxyalkyl, (1-10C)hydroxyalkyl, (1-10C)-fluoroalkyl having at least one fluorine provided that no fluorine is on a carbon bonded to a nitrogen, (2-10C)haloalkenyl having at least one halogen provided that no halogen is on a carbon bonded to a nitrogen; or R and R.sup.9 when taken together form a (4-6C)alkylene group wherein one of the carbons may optionally be replaced by an oxygen, or, when taken together, form a (4-6C)alkenylene group: PA0 R.sup.10 and R.sup.11 may be the same or different and are each hydrogen or (1-4C)alkyl; PA0 R.sup.12 and R.sup.13 may be the same or different and are each hydrogen, (1-4C)alkyl, (2-10C)acyl, or (4-10C)cycloalkylalkyl, provided that R.sup.12 may not be hydrogen when R.sup.3 is of formula (III) and R.sup.4 is OR.sup.12 ; and PA0 pharmaceutically acceptable salts and 1- or 2-position N-oxides thereof.
Unless otherwise specified, the alkyls, alkenyls and alkynyls described for this invention may be straight or branched chain. Aryl shall mean an organic radical derived from an aromatic hydrocarbon, e.g., phenyl. Aryl shall also include heterocyclic radicals, e.g., those derived from pyrrole, furan, thiophene, pyridine, thiazole or indole. Substituted amino includes mono- or di-substituted amines. Substituted aryls may be substituted with, for example, (1-4C)alkyl, (1-4C)alkoxy, or halogeno. The number of substitutions on an aryl may vary. For example, where the aryl has only one ring, for example phenyl, the number of substituents may be from 1 to 3. All of the substitutions are taken independently of each other; thus, a three member substitution from a listed group may include three different members, two of the same members or all identical members. The term halogeno includes fluoro, chloro, bromo and iodo.
A particular compound described in the EPO Application is 4-amino-8-phenyl-N-propyl-3-cinnolinecarboxamide as described in Example 92. This compound is shown as formula Ia.
(Formula set out on pages following Examples) Ia The use of this compound (or a salt thereof) as a binder to benzodiazepine receptors is the subject of this invention. A further use of this compound or a salt thereof is in antagonizing the pharmacological effects of benzodiazepine receptor agonists such as diazepam.
Pharmaceutically-acceptable salts of this compound, for example, physiologically acceptable acid-addition salts such as mineral acid salts, e.g., hydrohalides, especially hydrochlorides and hydrobromides, sulfates, nitrates and phosphates, or organic acid salts, for example, methanesulfonates, may also be used.
The present invention teaches the use of a compound of formula Ia or a non-toxic pharmaceutically acceptable salt thereof for the manufacture of a medicament for antagonizing the pharmacological effects of a benzodiazepine receptor agonist.
Synthetic methods for making a compound of formula Ia are described in the EPO Application, particularly Example 92, and also described in additional Examples below.
Pharmaceutical compositions of 4-amino-8-phenyl-N-propyl-3-cinnolinecarboxamide may be prepared according to methods known for the compounds cartazolate and tracazolate. Thus for the purpose of this invention a compound of formula Ia, or non-toxic physiologically acceptable salts, such as acid addition salts thereof, may be administered orally or parenterally in a conventional dosage form such a tablet, pill, capsule, injectable or the like. The dosage in mg/kg of body weight of compounds of the present invention in mammals will vary according to the size of the animal and particularly with respect to the brain/body weight ratio. In general, a higher mg/kg dosage for a small animal such as a dog will have the same effect as a lower mg/kg dosage in an adult human. A minimum effective dosage for a compound of formula Ia will be at least about 0.01 mg/kg of body weight per day for mammals with a maximum dosage for a small mammal such as a dog, of about 100 mg/kg per day. For humans, a dosage of about 0.01 to 12 mg/kg per day will be effective, for example, about 0.5 to 600 mg/day for an average man. The dosage can be given once daily or in divided doses, for example, 2 to 4 doses daily, and such dosage will depend on the duration and maximum level of activity of a particular compound. The dose may be conventionally formulated in an oral or parenteral dosage form by compounding about 0.5 to 250 mg per unit of dosage of conventional vehicle, excipient, binder, preservative, stabilizer, flavor or the like as called for by accepted pharmaceutical practice, for example, as described in U.S. Pat. No. 3,755,340. The title compound of the invention is also useful in the manufacture of pharmaceutical compositions for injection. Injectable compositions may be aqueous solutions, with or without pharmaceutically acceptable cosolvents (e.g. propylene glycol). Said compositions may be sterilized and/or contain adjuvants, such as preserving, stabilizing, or emulsifying agents, solution promoters, salts for regulating the osmotic pressure and/or buffers. The compound as used in this invention may be used in pharmaceutical compositions comprising a compound of formula Ia as previously described or be contained in the same formulation with or co-administered with one or more known drugs. Thus, an agent for antagonizing the effects of a benzodiazepine receptor agonist will comprise as an active ingredient a compound of formula Ia or a non-toxic pharmaceutically acceptable salt thereof.
The pharmacological activity and utility of the compound of formula Ia may be demonstrated by the following pharmacological tests: